Make your own crossover component, see images:#1 cut 1 more piece of Nylon/Kapton tape than the number of wires involved. (I use uninsulated 30AWG wire wrap wire)#2 layout the first wire to lead spacing needed#3 cover the first wire with a piece of tape with the carrier removed#4 repeat with the second wire#5 complete all wires until you are finished#6 form the wires and cut to length, I usually leave 1/10" overhang#7 take off the protector of the first piece of tape and stick to PCB. Solder in place#8 a sample of a simple X (crossover) component (full size)

EDIT:If you want, you can cover the crossover component with hot glue. Use freeze mist to cool glue down immediately.

There are times when making single sided boards that you may want to avoid multiple jumpers since some I.C.s. don't go just Pin 1 to Pin 1 etc.

This is not the best example, however, consider the simple crossover component on my finger tip (with no finger print). If I.C. X pin 1 goes to I.C. Y pin 2 and I.C. X pin 2 goes to I.C. Y pin 1, the crossover could be placed in-between the two I.C.s to accomplish this.

I would solder the crossover component on the foil side, just like a SMD resistor would be soldered.

Therefore the crossover component on the foil side contains the jumper(s) within itself.